Install the unmanaged package from the prework if you haven't already. Configure a named credential and remote site according to the specifications outlined in the business requirements. Enter the billing service credentials in the custom setting. install the Step 1 - unmanaged package present in a use case in your org for all users.
The purpose of this tutorial is to share my knowledge of exploiting common misconfigurations found in the popular CRM, Salesforce Lightning. As of current there is no public documentation on the attacker perspective.
As we know, Apex runs in a multitenant environment so to restrict the runaway apex code/processes to acquire shared resources, the Apex runtime engine strictly enforces these governor limits. These governor limits count for each Apex transaction. For each execution of a batch, these limits are reset in its execute method.
Whenever you choose to switch to salesforce, the first step is to decide which edition befits your requirements the most. It is an important process to understand salesforce features, limitations, and pricing as one wrong choice may result in such consequences that can't be undone.